Bristle setting



A 21, 1946. K. v. HARDMAN '2,406,7s2

- Filed Aug. 17, 1944 BY 'JZ/MWFKM Patented Aug. 27, 1946 Kenneth v.Hardman, Clifton, N. J.

Application August 17, 1944, Serial No. 549,838

This invention relates to bristle setting. It relates particularly to amethod and setting in which the cement used is forced by pressurebetween adjacent bristle butts and between the assembled butts and theinside of the ferrule at the time the cement is being hardened, so thatthe cement quickly fills space left by the bristles as they shrinkduring the curing or early stages of cooling subsequent to curing.

It is common practice to insert the ends of an assembly of bristleswithin a ferrule of a brush and set the bristles in position by means ofa cement that is hardened'byhe'at. In this usual practice, the cement inflowable condition is suitably applied initially to the bristle butts bydipping them in a solution of the cement, the volatile 5 Claims (01. s0o21) solvent used in the solution then evaporated,

and the cemented bristle butts then drawn into or otherwise fittedwithin the ferrule. In another common method, a cement is applied bypouring upon the bristle ends after they are in position within theferrule.

In any case, the cenient is hardened after application to the bristles.Common rubber cements are ordinarily used. They contain vulcanizationmaterial and the setting is effected by curing at elevated temperatures.4 i

Animal bristles as used contain an' amount of moisture that varies withthe humidity to which they have been exposed and is ordinarily about 8%.'During the curing some of this moisture is lost so that the bristlesshrink substantially. Also the rubber cement which is used shrinks alsoin curing. These shrinkages result in undependable securing of thebristles in the cement or undependablecementingof the outside of themass of cemented bristles within the ferrule.

The difliculty of properly securing the bristles within the ferrule andthe avoidance of rejects is sogreat that the dipping method whichotherwise would give the best setting, has been largely abandonedwithround or rigid ferrules infavor of the pouring method which, whilegiving not as good setting,is less apt to lead to second quality orrejected brushsettings because of the shrinkages referred to above.

Various expedients have been proposed to over,- come the dilficulty dueto the imperfect setting of the bristles within the ferrule of brushes.Thus, it has been proposed to taper the ferrule so that the settingafter curing may be driven down and thus wedged within the narrower partof the ferrule.

Also, it has been proposed to cure the setting incompletely so that theshrinkage is decreased as compared to the shrinkage obtained on completecuring. This expedient, however, leads to anew disadvantage, namely, thegreater susceptibility of the incompletely cured cement to attack bysolvents.

Another corrective that has been used is the nailing or riveting of theset butt ends of the bristles within the ferrule.

Also bristles have been dried before setting so that they expand onexposure later to normal atmospheric humidity. This effect, however, hasled in certain instances to deformation of the brush, the ferrulebecoming more rounded as the bristles absorb moisture and expand. 1

The present invention provides means for overcoming these disadvantagesand making a brush setting in which there is dependable satisfactoryholding of the bristles.

Briefly stated, the invention comprises the product resulting from andthe method of setting bristles within a ferrule or other holder with aheat hardenable cement that expands at the temperature of hardening, sothat the cement is pressed into the spaces available to it, against theends of the bristles assembled in the holder, and against the inside ofthe holder itself, all at the time the cement is undergoing hardening.In a preferred embodiment, the invention comprises such method andproduct in which the expanding cement used contains an elastomer of abutadiene copolymer and compounding ingredients including vulcanizationmaterial. The means preferred for causing the expansion of the cement isa blowing agent, that is, a compound that develops gas at thetemperature of curing of the cementing compound. I i

The invention will be illustrated by description in connection with thedrawing in which:

Fig. 1 is a perspective view of a brush in which the bristles aremounted in accordance with the present invention.

Fig. 21s a vertical section on line 22 of Fig. 1. Fig. 3 is a verticalsection .through a larger type of brush with wood insert member dividingthe bristles into two spaced series.

Fig. 4 is a fragmentary perspective view of the bristle mounting of kindused in Fig. 3.

Fig. 5 is a diagrammatic view showing in more detail the relation of thebristles to the cement in the brush mounting.

The spacing of the bristles from each other and also the spacing of thegas bubbles in a number of the figures are exaggerated for clearness ofillustration.

There are shown bristles 6 mounted in ferrules or holders 8, m, or H bymeans of cement [4 which, in the finished set condition, includesbubbles l6 that are ordinarily either diflicultly visible or microscopicin character but which are usually readily visible, as broken bubbles orcraters particularly, in the portion of the cement which, extends abovethe mounted ends of the bristles as in Figs. 3 and 4.

In one modification the brushes may contain a usual type of wood spacingbar is which separates the assembly of bristles into two parts andincreases the thickness of the brush for a given amount of bristlesused.

The ferrules may contain beads, such as shown at 2B and 2.2, into whichthe cementing compound is forced by the expansion at the time of settingas shown for example in Figs, 2. and 3.

In general the technique of mounting the bristles within the ferrule orother holder is that ordinarily employed except for the inclusion of anexpansion agent such as the blowing agent referred to. I

The blowing agent must be one which develops gas in the cementcomposition at the temperature required to harden the cement. Thus theremay be used diazoaminobenzene (Unicel), sodium bicarbonate, ammoniumcarbonate or carbamate. When a carbonate, carbamate or bicarbonate isused it is desirable to include in the cement compound a higher fattyacid. Such acid promotes the smooth and. uniform gassing and expansionof the compound at curing temperatures.

Diazoaminobenzene is preferred as the blowing agent. It has aplasticizing effect upon the cementing compound used and gives greaterinternal pressure than other expansion agents listed when the wholeassembly is cured.

The ferrule serves as a confining member to hold pressure upon thegassing cementing material and thus causes pressing of the cementingmaterial against the bristle ends and between the said ends and theferrule.

Any usual bristles may be used including those from hogs and horses, andsynthetic bristles such as those made from nylon or cellulose acetate.When particularly smooth, bristles such as those made from nylon areused, the ends that are to be mounted in the ristle setting arepreferably sanded before being treated with the cementing material, asdescribed in my copending application Serial No. 518,462, filed January15, 1944, and entitled Bristle treatment.

As the heat hardenable binder in the cementing compound, there may beused rubber or a heat hardenable synthetic rubber, as, for example, oneof the elastomers consisting of butadiene copolymers or polymerizedchloroprene (neoprene). Phenolaldehyde condensation products also may beused. Particularly satisfactory results and a large increase in thestrength and de pendability of the mounting are obtained when thecementing material used is a compound containing an elastomericbutadiene copolymer with usual compounding ingredients and a blowingagent of the class described above, the copolymers of butadiene withstyrene known commercially as Buna S being particularly desirable. Inlace of this particular butadiene copolymer, there may be used toadvantage also commercial copolymers of butadiene with otherpolymerizable monomers, say, Buna N, which is the copolymer of butadieneand acrylonitrile.

When the cementing material depends for hardening upon vulcanization ofrubber or other elastomer present, as, for instance, one of thebutadiene copolymers referred to, then the cementing compound shouldinclude compounding ingredients that are conventional in such elastomercompounds, including a vulcanization agent and suitably also avulcanization accelerator. Thus sulfur may be used as the vulcanizationagent in conjunction with any one of the common accelerators.

Also there is preferably used a plasticizer for the elastomer or theresin so that the compound until cured remains flowable althoughpreferably viscous and semi-plastic. Examples of plasticizers that maybe used include vulcanizable oils, aliphatic distillation pitches, coaltar resins, Bardol, vegetable oils or Naftolen 510.

Proportions of the conventional materials in the compound constitutingthe cement may be varied over rather wide proportions, to fit anyparticular hardness, rate of cure, or other property desired in thebristle setting, in a manner that will occur to one skilled in this art.

The blowing agent, on the other hand, must be used in proportionsufiicient to overcome the normal shrinkage of the binder on curing andgive the expansion necessary to cause the cement to expand to fill allspaces that should be filled by it and give good, pressed contact withthe bristle butts and with the inside surface of the ferrule. Thus,there may be used' to advantage 3 to 25 parts of diazoaminobenzene. Formost purposes sufiicient expansion and also economy of material are bothrealized when the proportion of the diazoaminobenzene is within therange 5 to 15% of the weight of the rubber component of the cementingcompound. When the blowing agent used is sodium bicarbonate or ammoniumcarbonate or carbamate, larger proportions of these less effectivematerials are used as, for instance, up to parts and preferably 40 to 80parts for parts of the Buna S or Buna N or other hardenable bindercomponent.

The ingredients which go to make the cementing material are compoundedin usual manner. Before application to the bristle ends to be mounted,the compound is ordinarily cut with a solvent to flowable viscosity.Thus, most of the cementing compounds may be and to advantage aredissolved in petroleum naphtha or the like. With certain other bindersthat are not soluble in petroleum hydrocarbons, there may be usedselected solvents that are known to dissolve the special binders. Thusthere may be used aromatic hydrocarbons, acetone, esters and the like,either alone or if necessary in mixtures with each other.

The invention will be further illustrated by description in connectionwith the following specific examples.

Erample 1 In setting bristles with a dipping cement, there is made acompound containing Buna S as the elastomer and sulfur in amountadequate to give on curing a hard vulcanisate with the accelera: tors,plasticizers or other compounding ingredients used. Thus there iscompounded with a usual mixing machine the following materials in theproportions shown.

Ingredient: Parts by weight Buna S 100 Diazoaminobenzene (Unicel) 1.0Sulfur 45 Benzothiazyl disulfide .2 Diphenylguanidine .8 Plasticizer(such as Naftolen #510) Dissolved in VM&P naphtha to dipping or pouringconsistency.

The Naftolen referred to as plasticizer is an unsaturated hydrocarbon,covulcanizable with-rubber and sulfur.

plasticizer and also bythe diazoaminobenzene which has a softeningeffect and increases the pliability of the Buna S ingredient of thecompound.

The proportion of sulfur in the above formula may be varied as, forinstance, from to 60 parts for 100 parts of Buna S.

Other conventional plasticizers for Buna S may be used, althoughNaftolen No. 510 is particularly satisfactory for the present purposes.Among other plasticizers that may be used are high boiling coal tarfractions'and resinous wood pitch.

Brushes which are set in the formula shown are heated to cure thecementing compound at 270 to The blowing agent used, namely,diazoaminobenzene, does not causeappreciable expansion of the compoundat the temperatures used for dryrule. e

-As a result of this internal pressure during the curing of the cement,the bristle setting has, a solid continuously fiuxed appearance on theends of the bristles whether natural or synthetic.

Example 2 The procedure of Example 1 is followed'except that the cementcompound is poured over the upper ends of the bristles after they arepoured into the ferrule. In this instance sufiicient volatile solvent isleft in the cement, at the time of pouring, to promote penetrationof'the cement a certain distance downward beween the, butt ends of thebristles.

Example 3 Th 'procedure of Example 1 is followed except that .there isused a compound including sodium 6 bicarbonate as theblowing agent. Thusthere is used as the cement a compound shown in the table below.

Ingredient: Parts by weight Buna N or Buna S 100 Tire sulfur 40 DPG .5,Altax .5 Sodium bicarbonate 50 to 80 Bardol 30 to 50 Dissolved inappropriate solvent such as toluene or VM&P.

At curing temperature the bicarbonate breaks down liberating carbondioxide gas which develops the desired internal pressure.

It will be understood that it is intended to cover all changes andmodifications of the examples of the invention herein chosen for thepurpose of illustration which do not constitute departures from thespirit and scope of the invention.

What I claim is: .1. The method of setting bristles within a ferrulewhich comprises fitting within the ferrule the ends of the bristlescomposited with a heat' hardenable, heat expansible cement in viscousbut fiowable condition, the cement being disposed between and outsidethe bristle ends, and then heating the assembly to the temperature ofhardening and expansion of the cement so as to cause expansion andhardening of the cement, the cement as used containing a material thatdevelops gas in the cement at the temperature of harden-- ing of thecement.

2. The method of setting bristles within a ferrule which comprisesfitting within the ferrule the ends of the bristles composited with aheat hardenable, heat expansible cement in viscous but fiowablecondition and then heating the assembly to the temperature of hardeningand expansion of the cement, so as to cause expansion and hardening ofthe cement, the cement containing a butadiene copolymer as the binderand a blowing agent that develops gas at the temperature of hardening ofthe said copolymer and the ferrule confining the cement during thegassing and thus causing pressing contact of the cement with the bristleends and with the inside surface of the ferrule at thetim of hardeningof the cement.

3. The method of setting bristles which comprises forming within aferrule an assembly of the ends of the bristles with a heat hardenable,

heat expansible cement in viscous but flowable condition, thecement'being disposed between and outside the bristle ends, and thenheating the assembly to the temperature of hardening of the cement so asto cause expansion and hardening of the cement, the cement being acompound j cluding the elastomeric copolymer of butadiene and styrene,vulcanization material, and a blowing agent that in the cement developsgas at the temperature of hardening of the cement and the ferruleconfining the cement during the development of gas.

4. The method described in claim 1, the material that develops the gasbeing diazoaminobenzene.

5. A brush setting comprising bristle ends fitted within a ferrule and avesicular cement in hardened condition pressed firmly against thebristle ends and against the inside of the ferrule.

KENNETH V. HARDMAN.

